Preparation And Properties Of Silicon Quantum Dots Modified MoX₂/rGO Composites

Energy depletion and environmental pollution are issues that need to be solved in the current social development.In recent years,two-dimensional transition metal chalcogenides（TMDCs）have been widely used in lubricants,optoelectronic devices,biosensing,and catalysis due to their weak interlayer interactions,large specific surface area,and controlled energy band structure.Two-dimensional MoS₂ and MoSe₂ as typical materials in two-dimensional TMDCs,with large bandgap,high theoretical specific capacity,and diversity of elemental valence states,have a good application prospect in the field of supercapacitors and photocatalysis,which provide an effective way for solving energy and environmental issues.However,they all have the disadvantages of easy agglomeration and poor conductivity.Therefore,this paper use the silicon quantum dots（SiQDs）to regulate the synthesis of MoS₂ and MoSe₂.And compositing with reduced graphene oxide（rGO）to overcome their shortcomings.First of all,this dissertation used silicon quantum dots（SiQDs）assisted hydrothermal synthesis of two-dimensional MoS₂,XRD,SEM,Raman and UV-Vis test analysis technology,explored the effect of SiQDs on product morphology,phase state,etc.Using the surface effect of zero-dimensional SiQDs as a nucleation center,MoS₂nanoflowering balls with good crystallinity and uniform morphology were grown,which effectively prevented the agglomeration of the sheets.The results show that SiQDs-MoS₂contains 1T and 2H phases,and its petals are ultra-thin,with a thickness of about 10 nm,and have a rich edge effect.It thus exhibits a strong full-spectrum absorption capacity and excellent photocatalytic degradation of malachite green（MG）.Within 100 min,the MG solution with a concentration of 10 mg/L was almost completely degraded.The degradation rate was in accordance with the first-order reaction kinetics equation.The rate constant k was 0.9919 min^-1.After 5 cycles,the catalytic activity could still maintain over 90%.Secondly,this dissertation prepared SiQDs-Mo S₂/rGO and SiQDs-MoSe₂/rGO composites,and investigated the effect of SiQDs on the structure of composites by XRD,SEM,and XPS,and speculated the mechanism of the regulation of SiQDs on the structure.The results show that in the MoS₂ composite system,SiQDs contribute to the development of MoS₂ from two-dimensional to three-dimensional,and evenly dispersed in two-dimensional rGO,and then form a special two-dimensional three-dimensional coexistence structure,showing excellent electrochemical performance.At a current density of 0.5 A/g,the specific capacitance is 947.5 F/g,and after 10,000 cycles,the specific capacity can still maintain 88.18%.In the composite system of MoSe₂,the addition of SiQDs can overcome the poor interface properties between MoSe₂ and rGO composites,forming a three-dimensional pore structure,and also exhibited excellent electrochemical performance 1 A/g.The specific capacitance at current density is 1148.5F/g,and after 10,000 cycles,the specific capacity can still maintain 78.91%.Both can be used as high-capacity,high-cycle stability supercapacitor electrode materials.In this dissertation,two-dimensional MoX₂（S,Se）was synthesized by SiQDs assisted hydrothermal synthesis,and then SiQDs-MoX₂/rGO composites with excellent electrochemical properties were prepared.It was used for the chemical synthesis of TMDCs and the new photocatalyst and supercapacitor electrode materials to preparation provides new ideas.